1. Field of the Invention
This invention relates to a half bearing constituting a cylindrical plain bearing when two of the half bearings are combined together.
2. Description of the Related Art
A plain bearing is used to support a rotating shaft such as a crankshaft of an internal combustion engine, for example. The plain bearing is made by combining two generally semicylindrical half bearings into a cylindrical form. A lubricating oil is supplied between an inner circumferential surface of the plain bearing and the rotating shaft so as to form an oil film.
Conventional half bearings constituting the plain bearing have crush relief surfaces formed on inner circumferential surfaces of both circumferential ends thereof respectively. The crush relief surfaces are formed so as to spread substantially over an entire width of the bearing or axial dimension of the bearing with respect to a shaft supported by the bearing. When a plain bearing is assembled into a bearing housing, joints of the respective half bearings sometimes shift from each other. Furthermore, when a crush height of the bearing is excessively high, the bearing is sometimes brought into a local contact with the shaft as the result of a radially inward swelling due to deformation in the vicinity of the joint. The aforesaid crush relief surfaces prevent the shift of the joints and the local contact. In the conventional half bearings, however, a large amount of lubricating oil leaks axially from each crush relief surface.
Therefore, an object of the present invention is to provide a half bearing which can reduce an amount of lubricating oil leaking therefrom with the function of the crush relief surface being maintained.
To achieve the object, the present invention provides a half bearing constituting a cylindrical plain bearing for supporting a shaft for rotation when two of the half bearings are combined together, the half bearing having two circumferential ends each of which has a plurality of circumferential grooves without formation of any crush relief surface, wherein the grooves extend substantially over an overall circumferential dimension of the half bearing and include portions located at both circumferential ends of the half bearinq respectively, each portion having a larger axially sectional area than the grooves formed in a portion of the half bearing mainly subjected to load during rotation of the shaft.
The half bearing is formed with a plurality of the circumferential grooves in the inner circumferential surfaces of both circumferential ends thereof although no crush relief surface is formed there. Protrusions defined between the grooves tend to be easily conformed to the shaft to be worn due to contact with the shaft. Accordingly, when the half bearings are combined together into a plain bearing, the protrusions are conformed to the shaft to be worn at an early stage such that worn portions serve as crush relief surfaces. Thus, the function of the crush relief surface can be achieved although the half bearing is formed with no crush relief surfaces. A region serving as the crush relief surfaces is minimum in this case. As a result, an amount of lubricating oil leaking in the half bearing can be smaller than in a case where a half bearing is positively provided with crush relief surfaces. Moreover, the half bearing can prevent an axial leakage of the lubricating oil more effectively since the grooves extend circumferentially.
Furthermore, the grooves extend substantially over an overall circumferential dimension of the half bearing and include portions located at both circumferential ends of the half bearing respectively. Further, each said portion has a larger axially sectional area than the grooves formed in a portion of the half bearing mainly subjected to load during rotation of the shaft. A large amount of lubricating oil can be supplied without reduction in a load capacity of the portion mainly subjected to load during rotation of the shaft. Consequently, an anti-seizure property and a sliding characteristic can be improved.
In a preferred form, said portions of the grooves located at both circumferential ends respectively are deeper than the grooves formed in the portion of the half bearing mainly subjected to load during rotation of the shaft. In addition to the effect of increasing an amount of lubricating oil fed to the portion mainly subjected to the load, the protrusions located at both circumferential ends tend to be easily conformed to the shaft to be worn with contact with the shaft since the protrusions have a lower strength than those located between the grooves of the portion mainly subjected to the load during rotation of the shaft.